The enzymatic synthesis of dimethyl-8-ribityllumazine, the immediate precursor of riboflavin, from 5-amino-2,6-deoxy-4-ribitylaminopyrimidine (ADRAP) will be investigated. For this purpose, extracts of the bacterium Photobacterium phosphoreum, an over producer of dimethyl-8-ribityllumazine, will be used as a source of enzymes. The enzyme system will be purified, separated, studied individually, and possible intermediates will be identified. The work on the biosynthesis of the pteridine pigments in the fruit fly, Drosophila melanogaster will be continued. The enzyme system which is necessary for the conversion of dihydroneopterin triphosphate to drosopterin will be further purified with the goals of identifying biosynthetic intermediates and shedding some light on the chemistry of this complex transformation. We shall also continue our work on the characteristics and functions of specific pterin-metabolizing enzymes in Drosophila. For example, the enzyme "dihydropterin oxidase", which we have purified to approximately 50% purity will be further investigated as regards its physiological function and its chemical characteristics.